When Adrienne S. Ettinger started her first job out of graduate school in public health in 1991, there were an estimated 1.7 million American children with high levels of lead in their blood.

Ettinger would know. She went looking for them in inner-city New Jersey, knocking on doors and asking residents to join studies on home cleaning for lead dust — studies that could help protect children living there. She recalls being struck by people’s openness and willingness to participate.

“It was really amazing how these people would let us into their homes and to every detail of their lives,” says Ettinger, assistant professor in the Department of Chronic Disease Epidemiology. “Your home is your safe place.”

Except, of course, when it isn’t. Many of us are menaced at home not only by lead but also by toxic gases, allergens and worse.

Such hazards are Ettinger’s specialty. In a long career as an environmental epidemiologist, she has focused on housing-related hazards, grappling with substances that may be useful in some contexts but also pose insidious threats in and around our own homes. She has found that mothers living near hazardous waste sites have chemical contaminants in their breast milk. She has also played an important role in managing these hazards nationwide by training workers to think beyond individual problems and focus on the whole home.

In some ways, the home environment is getting safer. The last few decades, for example, have seen a drastic decline in the number of American children with high blood lead levels (BLLs). But Ettinger and her fellow epidemiologists say the task is by no means complete — not for lead, and not for a number of other indoor hazards.

And new threats surface all the time.

Lead’s legacy

Lead is a classic example of a double-edged sword. Added to paint, it produced a durable, washable finish; in gasoline, prior to the catalytic convertor, it improved gas mileage and engine efficiency. It is a crucial ingredient of car batteries, makes an excellent radiation shield, and is tremendously useful in building construction.

Yet it is also a notorious neurotoxin, one that does its damage slowly and all but invisibly. Even at low levels, lead exposure can cause learning disabilities or behavior problems that reduce a child’s chances of educational success. And though lead is no longer used in paint or gasoline in the United States, untold tons of it remain in the environment.

Just how to reconcile these realities is a problem that has occupied Ettinger and other researchers for years. The Centers for Disease Control and Prevention’s (CDC) Healthy Homes/Lead Poisoning Prevention Branch (HHLPPB),where Ettinger worked in the mid-1990s, for example, convenes a federal advisory committee of scientists, advocates and health department officials to discuss lead toxicity as well as other home-based threats. It is the members of this committee who set national guidelines for pediatric blood-level testing and recently lowered the limit of concern. Ettinger, meanwhile, recently oversaw the CDC working group that developed guidelines to identify and manage elevated BLLs in pregnant and lactating women.

While blood tests may reveal lead hotspots, practitioners have to strike a careful balance between eliminating lead from the home and mitigating the hazard it poses. Total lead removal is expensive, and the process can disturb lead so that it may do more harm than good if not done properly. In many cases, it’s better to use such interim control strategies as covering painted surfaces and advising residents to control dust in their homes or flush pipes before drinking their water.

“We made a decision as a country in the early 1990s that we were going to make housing lead-safe, not lead-free,” says program head Mary Jean Brown, Sc.D., R.N., who is the former chief of the CDC’s Lead Poisoning Prevention Branch. “That means that for the foreseeable future, we are going to live with this toxin in our midst.”

Statistics suggest that this relatively modest strategy has paid off. A late 1970s survey found that 88 percent of children between ages 1 and 5 had BLLs greater than 10 micrograms per deciliter (mcg/dL). In the late 2000s, less than 1 percent did. And the reduction has been the most pronounced in African-American and poor children, groups with historically higher blood lead levels — which raises issues of environmental justice. Children who have dodged the lead bullet stand a far better chance in life. Today, about half a million American children still have blood lead levels of 10 mcg/dL or higher — a large and tragic number, but a sign of progress nevertheless.

“With lead [abatement], you get an amazing return on your investment, and we know exactly what to do,” says Rebecca Morley, executive director of the National Center for Healthy Housing (NCHH), formerly the National Center for Lead-Safe Housing.

Successes, challenges

And yet Ettinger cautions that it’s too soon to declare victory.

Although lead was banned from gasoline and paint in the 1970s, some 38 million units of housing still contain aging lead paint, while much of the soil in urban areas is contaminated by decades of lead emissions from the leaded gasoline era.

Lead from both sources can be inhaled or ingested. When a person takes lead into the body, it accumulates in the tissues, mainly in bone where it will remain for decades and can leach out during pregnancy and cross the placenta. In exposed fetuses, as well as in children who chew paint flakes or a lead-coated toy, lead can cause gradual and irreversible brain damage. The work of Ettinger and colleagues has found that pregnancy and breastfeeding can increase the intergenerational risks for exposure to such environmental contaminants as lead, and that those exposed in the womb may be at greatest risk during the first trimester.

Indeed, no blood lead level appears to be safe in children, so the CDC announced in 2012 that a BLL of 5 mcg/dL should trigger a clinical follow-up. Even levels as low as 2 or 3 mcg/dL raise the risk of poor academic performance and attention-deficit disorder.

Amid the new standards, however, the CDC’s lead-fighting resources have been slashed. The HHLPPB’s 2012 budget was cut to just 7 percent of its 2011 budget, forcing it to withdraw financial support for state and local lead-prevention programs. “Unfortunately, the message about our public health success in this area has been communicated as a ‘job well done,’ when in fact the job is far from being done,” says Morley.

To keep up with dwindling resources, tighter standards, and a shift in public attention, public health programs are changing their approach. Although decades of screening children with blood tests have allowed officials to target problem housing, testing doesn’t offer much to the children themselves because the benefits of therapies like chelation are modest at best. The goal now is to prevent childhood lead exposure entirely — primary prevention — which means a shift toward screening houses, not children, for lead contamination. The hope is to nip lead problems in the bud.

A holistic approach

Even as scientists work to prevent lead poisoning, they’re stepping back to look at what else is wrong with our homes. Why stop with lead and pronounce a house “safe” if it also has fire-prone wiring or rampant allergens or excessive use of pesticides?

In the early 2000s, Ettinger, then a Johns Hopkins faculty member, began to work with the NCHH to develop guidelines for what constitutes healthy housing. “Certain toxic exposures, like lead and tobacco, had their own prevention programs, while others, such as mold and pesticides, were emerging as concerns,” she recalls. “Nobody was really taking a holistic look at the home from a health perspective.”

Under that nonprofit’s auspices and with CDC support, Ettinger and colleagues developed curricula in broad healthy housing principles for public health, housing and energy efficiency professionals. Some 20,000 have since been trained across the country. Today’s HHLPPB is similarly holistic. Its goals include not only the elimination of high BLLs in children but also ensuring that a house’s location, design, construction, maintenance and renovation support the residents’ health.

That’s a huge undertaking. Radon gas alone kills 22,000 people a year from lung cancer — more than twice the number killed by drunk drivers. Carbon monoxide and secondhand smoke continue to foul indoor air. Many houses are permeated by asthma triggers like mold, pesticides and cockroach dander. Carpets emit toxic fumes, as do many substances in newly constructed homes — which was demonstrated by some of the post-Katrina FEMA trailers when they offgassed formaldehyde. Children fall through unguarded high-rise windows and elderly people fall down stairwells when handrails are broken or missing.

Despite limited funds, the HHLPPB is working with the Department of Housing and Urban Development on secondhand smoke, allergens, and ventilation, and with the CDC’s Injury Center on home injuries. The branch maintains an advisory board and a national surveillance system, and it works with epidemiologists to respond to reports of lead in consumer products (in recent months, those have included pirate costumes and eye makeup). The HHLPPB also serves as a federal partner to the training center.

Committing to the big picture in environmental epidemiology may go beyond understanding individual hazards; what’s also needed are a cross-disciplinary approach and a search for unconventional solutions. For example, environmental health and perinatal epidemiology are often housed in distinct academic silos, yet many environmental toxins act on the fetus. Yale’s Center for Perinatal, Pediatric and Environmental Epidemiology (CPPEE), combines these academic disciplines. Ettinger’s colleagues at CPPEE, including co-directors Michael B. Bracken, M.P.H. ’70, Ph.D. ’74, and Brian P. Leaderer, M.P.H. ’71, Ph.D. ’75, are studying the effects of household levels of nitrogen dioxide from gas stoves, and such respiratory effects as asthma in children. That broad outlook drew Ettinger, an experienced perinatal researcher, to join the Yale faculty in 2010.

After years of studying fetal exposure to lead, arsenic, and other hazardous substances, Ettinger has recently begun to look at solutions to indoor health hazards from a nutritional angle. The idea is that if engineering fixes are expensive and impractical, eating protective foods or dietary supplements may offer another way to reduce harm. In pregnant women with high bone lead levels, for example, Ettinger has shown that calcium supplements may partially protect the fetus and nursing infant from lead exposure.

Finding balance

Can we look forward to safer homes in the future?

Morley is optimistic, noting that people are getting savvier about their options and that improved transparency is allowing for more choices. “I think that consumers are on to industry,” she says. “It’s going to be in industry’s best interest to adopt some of these practices for marketing differentiation and for liability protection.” Yet the NCHH’s attempts to speed changes are often frustrated. When the nonprofit proposes safety-related updates to building codes before the International Code Council (ICC), Morley says, it meets with opposition — from the National Association of Home Builders.

Indeed, we seem to take two steps forward and one step back with some hazards. Take energy efficiency: though post-1970s homes are more efficient thanks to tighter construction and more seamless insulation, sealing in heat and air conditioning comes at a cost; toxic substances in the air don’t vent as readily and indoor air quality suffers. Mere awareness and the availability of such tests as the one for radon aren’t sufficient to eliminate problems. Ettinger is also concerned about the potential dark side of useful things like Teflon-coated pans, such plasticizers as BPA and phthalates, indoor pesticides and a myriad of personal care products. And despite all we know about lead, it keeps cropping up where we shouldn’t expect to see it any longer. Constant vigilance is in order.

“Twenty years ago my thesis advisor was being interviewed about lead in lipstick, and now it’s in the news again,” Ettinger says. “There’s a lot that still needs to be done.”

Though it can be hard to abate known hazards, the bigger problem according to Ettinger is simply a lack of knowledge. There are hundreds of thousands of synthetic chemicals on the market, and the health effects of the vast majority are unknown. Decision making may be made harder by groups that advocate blanket avoidance of artificial substances, casting an alarmist light on innovation and subtracting nuance from policy discussions. Yet when we do find that a specific chemical causes harm, Ettinger said, manufacturers often react by changing one of its molecules to create a similar but unstudied substance.

“We need well-conducted peer-reviewed research done by scientists in order to answer these questions,” she says.

From a public health perspective, then, it’s important to neither overlook nor oversimplify indoor hazards. Case in point: the two-sided health effects of chlorine in drinking water, which bears some similarities to our relationship with lead. The substance kills harmful bacteria, preventing potentially deadly waterborne illnesses, yet the byproducts of chlorination that we breathe in during a hot shower or consume in drinking water, for example, can themselves be harmful. There is, it seems, no escaping the big picture.

“It’s not a question of right or wrong,” Ettinger says. “It’s about weighing the risks and getting everything in balance.”

This article originally appeared in the Fall 2013 issue of Yale Public Health magazine. The magazine can be viewed here.